Most replacement tools has onl single line support, so do Regexxer too. It would be great if multiline support (not only by inserting \n) will be added to Regexxer.
Some screens of tool with multiline support:
http://web-search-and-replace.smartcode.com/images/sshots/web_search_and_replace_23759.gif
http://www.iknowkungfoo.com/images/blog/eclipse_file_search_03.gif
http://filedb.experts-exchange.com/incoming/2008/09_w39/62953/reg-expression-template-code-rem.jpg